Subaru Legacy 2003 Service Manual page 644

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK OPERATION OF BRAKE LIGHT.
Does brake light come on when depressing the
brake pedal?
2 CHECK HARNESS BETWEEN TCM AND
BRAKE LIGHT SWITCH CONNECTOR.
1) Disconnect connectors from TCM and
brake light switch.
2) Measure resistance of harness between
TCM and brake light switch connector.
Connector & terminal
(B55) No. 12 — (B64) No. 2:
(B55) No. 12 — (B65) No. 3 (With cruise
control):
Is the measured value less than the speci-
fied value?
3 CHECK HARNESS BETWEEN TCM AND
BRAKE LIGHT SWITCH CONNECTOR.
Measure resistance of harness between TCM
and chassis ground.
Connector & terminal
(B55) No. 12 — Chassis ground:
Does the measured value exceed the specified
value?
4 CHECK INPUT SIGNAL FOR TCM.
1) Connect connectors to TCM and brake light
switch.
2) Measure voltage between TCM and chas-
sis ground.
Connector & terminal
(B55) No. 12 (+) — Chassis ground ( − − − − ):
Is the measured value less than the speci-
fied value when releasing the brake pedal?
5 CHECK INPUT SIGNAL FOR TCM.
Measure voltage between TCM and chassis
ground.
Connector & terminal
(B55) No. 12 (+) — Chassis ground ( − − − − ):
Is the measured value less than the specified
value when depressing the brake pedal?
6 CHECK POOR CONTACT.
Check poor contact in TCM connector.
Is there poor contact in TCM connector?
Value
Brake light comes on.
1 Ω
1 MΩ
1 V
10 V
There is poor contact.
EN(H4SO)-247
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair or replace
brake light circuit.
Go to step 3. Repair or replace
harness and con-
nector.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
TCM and brake
light switch con-
nector
• Poor contact in
TCM connector
• Poor contact in
brake light switch
connector
Go to step 4. Repair ground
short circuit in har-
ness between
TCM and brake
light switch con-
nector.
Go to step 5. Adjust or replace
brake light switch.
<Ref. to LI-8, Stop
Light System.>
Go to step 6. Adjust or replace
brake light switch.
<Ref. to LI-8, Stop
Light System.>
Repair poor con- Replace TCM.
tact in TCM con- <Ref. to AT-76,
nector. Transmission Con-
trol Module
(TCM).>
No